iptables.rule为firewall总规则；
iptables.allow为充许进入的主机；
iptables.deny为不许放的主机；
iptables.allow代码如下：
#！/bin/bash
# This is an esay firewall.
# the inside interface. if you don't have this one
# and you must let this be black ex> INIF=""
INIF="eth0"
INNET="192.168.160.0/20"
# 2.0 load the right module
PATH=/sbin：/bin：/usr/sbin：/usr/bin
export PATH EXTIF INIF INNET
modprobe ip_tables > /dev/null 2>&1
modprobe iptable_nat > /dev/null 2>&1
modprobe ip_nat_ftp > /dev/null 2>&1
modprobe ip_nat_irc > /dev/null 2>&1
modprobe ip_conntrack > /dev/null 2>&1
modprobe ip_conntrack_ftp > /dev/null 2>&1
modprobe ip_conntrack_irc > /dev/null 2>&1
# 3.0 clear iptables rule
/sbin/iptables -F
/sbin/iptables -X
/sbin/iptables -Z
/sbin/iptables -F -t nat
/sbin/iptables -X -t nat
/sbin/iptables -Z -t nat
/sbin/iptables -P INPUT DROP
/sbin/iptables -P OUTPUT ACCEPT
/sbin/iptables -P FORWARD ACCEPT
/sbin/iptables -t nat -P PREROUTING ACCEPT
/sbin/iptables -t nat -P POSTROUTING ACCEPT
/sbin/iptables -t nat -P OUTPUT ACCEPT
# 4.0 start loading trusted and denied file.
if [ -f /usr/local/virus/iptables/iptables.allow ]； then
sh /usr/local/virus/iptables/iptables.allow
fi
if [ -f /usr/local/virus/iptables/iptables.deny ]； then
sh /usr/local/virus/iptables/iptables.deny
fi
# 5.0 if the following file exist ，please executed
if [ -f /usr/local/virus/httpd-err/iptables.http ]；then
sh /usr/local/virus/httpd-err/iptables.http
fi
# 6.0 allow icmp data packet and the establishd data
/sbin/iptables -A INPUT -m state ——state ESTABLISHED，RELATED -j ACCEPT
AICMP="0 3 3/4 4 11 12 14 16 18"
for tyicmp in $AICMP
do
/sbin/iptables -A INPUT -i $EXTIF="eth0" -p icmp ——icmp-type $tyicmp -j ACCEPT
done
# 7.0 open the other service ports
/sbin/iptables -A INPUT -p TCP -i $EXTIF="eth0" ——dport 25 -j ACCEPT # SMTP
/sbin/iptables -A INPUT -p TCP -i $EXTIF="eth0" ——dport 53 -j ACCEPT # DNS
/sbin/iptables -A INPUT -p TCP -i $EXTIF="eth0" ——dport 80 -j ACCEPT # WWW
/sbin/iptables -A INPUT -p TCP -i $EXTIF="eth0" ——dport 110 -j ACCEPT # POP3
/sbin/iptables -A INPUT -p TCP -i $EXTIF="eth0" ——dport 113 -j ACCEPT #AUTH
/sbin/iptables -A INPUT -p TCP -i $EXTIF="eth0" ——dport 22222 -j ACCEPT #SSH
/sbin/iptables -A INPUT -p UDP -i $EXTIF="eth0" ——dport 138 -j ACCEPT #138
/sbin/iptables -A INPUT -p TCP -i $EXTIF="eth0" ——dport 139 -j ACCEPT #139
/sbin/iptables -A INPUT -p UDP -i $EXTIF="eth0" ——dport 137 -j ACCEPT #137
/sbin/iptables -A INPUT -p TCP -i $EXTIF="eth0" ——dport 445 -j ACCEPT #445
iptables.allow代码如下
#！/bin/bash
# this program is used to allow some IP or hosts to access your server
/sbin/iptables -A INPUT -i $EXTIF="eth0" -s 192.168.161.242 -j ACCEPT
/sbin/iptables -A INPUT -i $EXTIF="eth0" -s 192.168.160.178 -j ACCEPT
/sbin/iptables -A INPUT -i $EXTIF="eth0" -s 192.168.160.218 -j ACCEPT
iptables.deny代码如下
#！ /bin/bash
# This script will deny some IPs that I don't want in IN
/sbin/iptables -A INPUT -i $EXTIF="eth0" -s 192.168.160.242 -j DROP
以上的三个文件都放在/usr/local/virus/iptables目录下，最在修改此文件/etc/rc.d/rc.local成如下代码。
#！/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
touch /var/lock/subsys/local
# Starting firewall settings
/usr/local/virus/iptables/iptables.rule
以上就是linux下firewall简易设置啦。